Suspicion for the apparent shooting down of a Malaysia Airlines flight immediately fell on pro-Russian separatists in eastern Ukraine who two weeks ago boasted of capturing powerful surface-to-air missiles.

Anton Gerashenko, a senior aide to Ukraine's interior minister, said the aircraft carrying 295 passengers was brought down with a missile fired from a Buk anti-aircraft missile battery.

Fighters from the Donetsk People's Republic (DPR) overran a Ukrainian army garrison on June 29 and claimed to have captured at least one such weapon.

The DPR posted a Twitter picture of the missile system, which is mounted on the back of a vehicle and would easily be able to bring down a slow-moving commercial airliner flying in a straight line.

A spokesman told Voice of Russia radio at the time: "The forces of the Donetsk People’s Republic assumed control of A-1402 [regiment's] military base" and boasted of capturing the Buk launcher.

A similar weapon was reportedly seen by an Associated Press journalist on Thursday in the town of Snizhne, a separatist-held area within the DPR.

As word spread of the crashed Malaysia Airlines flight on Thursday, the separatists deleted the Twitter photograph of the captured missile system.

Wreckage of the Malaysian Airlines plane which was carrying 295 people from Amsterdam to Kuala Lumpur (Getty)

Andrei Purgin, the self-declared deputy prime minister of the DPR, furiously backtracked and denied that his forces had any such weapons.

"Of course, we do not have such systems.These arms are too heavy and too powerful,we simply have nowhere to get them," he told the Interfax news agency.

The Buk missile system was designed by the Soviet Union in the late 1970s to bring down Nato aircraft and remains a staple of the Russian military arsenal.

Amid the confusion over the Malaysia Airlines flight, US intelligence is still investigation the case of a Ukrainian cargo jet which was shot down on Monday.

The An-26 transport jet was flying at 21,000 feet, lower than the Malaysia Airlines Boeing-777 would have been going, when it was apparently brought down by a surface-to-air missile.

"Only very sophisticated weapons systems would be able to reach this height," said a US official.

People stand next to the wreckages of the malaysian airliner carrying 295 people from Amsterdam to Kuala Lumpur after it crashed (Getty)

American intelligence is still unclear over whether the transport jet was brought down by Ukrainian separatists armed with powerful weapons or by the Kremlin's military forces massed on the Russian side of the border.

The Ukrainian government claimed that one of its fighter aircraft was brought down by Russian fighter jet on Wednesday.